Water's boiling point is 212F, yet there is still water in the kettle after boiling for over an hour.

Chlorine is highly volatile at standard temperature and pressure. In fact it prefers to be a gas. But water, not so much. Water has a high "heat of vaporization" at standard temperature and pressure, and can only evaporate up to 100% relative humidity near the kettle, beyond which it evaporates and recondenses at the same rate. It would much rather be liquid water at standard temperature and pressure, but will reluctantly convert to vapor with a lot of energy.

Yes, chlorine (which is actually a very low concentration in the form of hypochlorite which degrades to form chlorine gas) will evaporate out of water to non-detectable levels at standard temperature and pressure if left overnight prior to brewing.

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Dave

The world will become a much more pleasant place to live when each and every one of us realizes that we are all idiots.

Brewing season for me tends to be after marching band season ends until just before the weather gets hot again. It used to be based on ground water temp but now it is driven by my kids schedule. I usually have more beer on hand than I can consume anyway so I don't need to brew all year.